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The review paper presents the various passive methods used in the heat exchanger in detail with their advantages and disadvantages over the active methods. The paper studies the experimental and numerical studies of twist tape as an insert due to its retrofit capability and easy handling advantages. The experimental studies are categorized based on the geometrical parameter of the twist tape insert. The twisted tape with similar geometries is compiled in the same section. For example, twist tape with a clockwise twist, anticlockwise twist, alternate twist, or twist tape with a twist and no twist in the same section. It is a concise form that basically illustrates the studies based on similar geometrical parameters. The study covers both experimental and numerical studies and presents the advantages of experimental and numerical studies over one another. There is a section that shows statistical analysis of the Nusselt number and friction factor for various swirl flow inserts with comparison to the plain tube. The selection of twist tape inserts for the heat exchanger depends upon the cost and feasibility at the required point of application of the heat exchanger. This is done by comparing the thermal performance factor of the insert in the heat exchanger. The thermal performance factor of a particular insert in a tubular heat exchanger must be greater than 1, to justify its capability as a good insert. Finally, future recommendations are suggested to further carry out the work in this domain. [ABSTRACT FROM AUTHOR]

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Thermal engineering experiments were carried out with laboratory water-to-water tube-in-tube heat exchangers of the same design parameters with smooth and profiled inner tubes. The tubes were profiled by confuser–diffuser constrictions of the flow section of the inner channel, which were formed by the deformation of their walls and placed along the length at a step that was constant and equal for all profiled tubes. The obtained results showed a dependence of the heat transfer enhancement in the tube channel on the Reynolds and Prandtl numbers, with the dependence on the latter being much stronger than that on the former, at least in cases where the heat carrier is water. [ABSTRACT FROM AUTHOR]

The results of thermal engineering experiments on a water–water tubular heat exchanger of the tube-in-tube type with heat transfer intensified by periodic confuser–diffuser elements arranged along the channel length at a step equal to the doubled inner diameter of the inner tube are compared with the results of experiments on a similar smooth-tube heat exchanger and the results of calculations by the criterial models of B.S. Petukhov, S.S. Kutateladze, W. Nusselt, and M.A. Mikheev. The comparison showed that the ratio of heat transfers in the tube channels of the intensified and smooth-tube heat exchangers, being a function of the Reynolds and Prandtl numbers, depends on the latter to a much higher extent. As a consequence, at least for water as a medium where the Prandtl number depends on temperature, the intensification of heat transfer is determined not only by the profiling parameters, but also by the parameters of the heat transfer process itself. In addition, the comparison demonstrated that the replacement of experimental data on smooth-tube heat exchangers by the results of calculation by the criterial models worsens the accuracy of estimates and leads to an increase in deviations with an increase in the Reynolds number Re. [ABSTRACT FROM AUTHOR]

It is known that the results of calculations for various criterial models of convective heat transfer may differ from each other, which, according to existing ideas, is usually associated with different operating conditions of the heat exchangers under study. In the work, thermal engineering experiments are carried out with a laboratory water-to-water tubular heat exchanger of the "pipe-in-pipe" type with smooth tubes at normal pressure and moderate temperatures at various inlet temperatures of the heat carriers and their flow rates. The results of the experiment are compared with the results of calculations based on the models of B.S. Petukhova, S.S. Kutateladze, Nusselt, and M.A. Mikheev. The comparison shows that the discrepancies between the experiment and the models, as well as between the models themselves, stem not only from experimental inaccuracies, but also from inaccuracies in the models themselves. [ABSTRACT FROM AUTHOR]

Copyright of Eurasian Physical Technical Journal is the property of E.A. Buketov Karaganda University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The processing of dimple on the outer wall of tube will produce corresponding protrusion dimple on the inner wall. The turbulent flow and heat transfer performance of a tubular heat exchanger containing a dimpled inner tube is studied numerically. The results show that the main reason for the enhancement of heat transfer ability of the dimple is the flow vortex in the concave dimple and the shock to the wall induced by the protrusion dimple. Compared with the smooth wall of the tube, the maximum enhancement of heat transfer was 1.94 times in concave dimple and 2.74 times in protrusion dimple. By comparing the heat transfer performance, flow resistance, and comprehensive heat transfer factor of the tube and shell of different sizes of exchange heat pipe, it is determined that the combination of inner and outer wall dimple size of 10–15 mm is a structure with better comprehensive heat transfer performance. [ABSTRACT FROM AUTHOR]

Since it is known that the results of calculations for various criterial models of convective heat transfer may differ from each other, we compare the experimental data on heat transfer obtained in experiments on laboratory water-to-water tubular heat exchangers with smooth tubes of three different diameters at normal pressure and moderate temperatures with the results of calculations for the criterial models of B.S. Petukhova, S.S. Kutateladze, Nusselt, and M.A. Mikheev. The experiments are carried out on a two-dimensional flow grid of a tube and inter-tube channel, which makes it possible, in accordance with the previously developed method, to construct the longitudinal profiles of the heat-exchange parameters. The results of processing of the experimental data using the method of average values and the longitudinal profiles demonstrate good agreement when compared with each other. It is found that the deviations of the experimental data from the results of calculations using criterial models are systematic in nature; depend on the range of the defining parameters, i.e., the Reynolds and Prandtl numbers Re–Pr in which they are compared; increase with increasing Re number; and, depending on the Pr numbers, have an extremum. [ABSTRACT FROM AUTHOR]

This paper aims to present a numerical study on heat transfer enhancement of a tubular heat exchanger inserted with novel anti-clockwise clockwise twisted (ACCT) tape. Twelve different combinations of ACCT tapes are investigated; including tapes with four twist ratios (x/b) and three twist angles (θ) in a turbulent flow zone (4000 ≤ Re ≥ 24000). Parametric analysis is carried out to understand the flow characteristics. The results revealed that the proposed insert develops multiple vortices in the flow, increasing the turbulent kinetic energy. The Nusselt number, friction factor and thermal performance factor (TPF) of the tube with ACCT tapes increases with the increasing twist angle and the decreasing twist ratio. The highest enhancement of the Nusselt number and friction factor by 2.98 and 6.86 times is achieved for ACCT tapes with x/b = 3.0, θ = 90° and Reynolds number of 4000. The TPF is above unity for all the considered cases, with the highest being 1.54, verifying that use of the ACCT tapes is an efficient technique. Further by selecting the appropriate twist angle and twist ratio for the ACCT tape, a beneficial balance between increased heat transmission rate and friction factor can be achieved. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Institute of Science & Technology / Iğdır Üniversitesi Fen Bilimleri Enstitüsü Dergisi is the property of Igdir University, Institute of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Failure analysis of a tubular oil heat exchanger made up of admiralty brass in an industrial unit was investigated. In the oil exchanger, circulating water is used as a coolant inside the brass tubes to reduce the temperature of oil flowing inside the brass shell. The causes of failure of the leaked admiral tubes were investigated performing various visual and microscopic examinations. Chemical analysis of the corrosion scales and its phase analysis with x-ray diffraction and microstructural examinations by optical and scanning electron microscopy were carried out. The study revealed that tube material was suffering from extensive de-zincification and under-deposit pitting. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of static and dynamic neural network (NN), model to predict the exit temperature of the heat exchangers. Feed forward NN was used as a static network while Time delay NN was used for a dynamic network. Experimental data was collected from a shell and tube heat exchanger to provide sufficient data processing, namely training, test and validation data to develop the models. The static and dynamic network models of the heat exchanger have been developed using Matlab. The performances of the models were evaluated by their statistical validity using the correlation co-efficient and the mean squared error. For time series predictions, the dynamic NN has shown better results than the static NN. [ABSTRACT FROM AUTHOR]

Modeling of the process of thermal fluidization of a ventilated granular bed by means of a heat exchanger in the form of horizontal tubes positioned inside the bed is carried out. [ABSTRACT FROM AUTHOR]

The problem of synthesis of feedback control for objects with distributed parameters using continuous monitoring of the phase state of an object at its definite points is considered and illustrated by the example of control of the process of heating a tubular heat exchanger in its steam jacket. To solve the problem, it is proposed to use first-order numerical methods. Formulas for components of the gradient of an objective functional in the space of the parameters being optimized are derived. The results of the made numerical experiments are presented. [ABSTRACT FROM AUTHOR]

A regenerative gas turbine cycle with two particular tubular recuperative heat exchangers in parallel is considered for multi-objective optimization. It is assumed that tubular recuperative heat exchangers and its corresponding gas cycle are in design stage simultaneously. Three objective functions including the purchased equipment cost of recuperators, the unit cost rate of the generated power, and the exergetic efficiency of the gas cycle are considered simultaneously. Geometric specifications of the recuperator including tube length, tube outside/inside diameters, tube pitch, inside shell diameter, outer and inner tube limits of the tube bundle and the total number of disc and doughnut baffles, and main operating parameters of the gas cycle including the compressor pressure ratio, exhaust temperature of the combustion chamber and the air mass flowrate are considered as decision variables. Combination of these objectives anddecision variables with suitable engineering and physical constraints (including NOx and CO emission limitations) comprises a set of mixed integer non-linear problems. Optimization programming in MATLAB is performed using one of the most powerful and robust multi-objective optimization algorithms, namely non-dominated sorting genetic algorithm. This approach is applied to find a set of Pareto optimal solutions. Pareto optimal frontier is obtained, and a final optimal solution is selected in a decision-making process. [ABSTRACT FROM AUTHOR]